Pumping system and method for recovering fluid from a well

ABSTRACT

The present invention relates to a pumping system and method for drawing or pumping subsurface fluid (e.g., gas, oil, water, etc.) from a well, particularly a gas well. The pumping system of the present invention includes a pump which displaces fluid in a well into a string of hollow sucker rods during the downward stoke of the pump. The string of hollow sucker rods extends generally to the surface so that the fluids can be directed to collection equipment on the surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

The present invention relates generally to pumping systems forrecovering or pumping subsurface liquids from a well.

When hydrocarbon-producing wells are drilled, initial hydrocarbonproduction is usually attained by natural drive mechanisms which forcethe hydrocarbons into producing wells. Further, as the reservoir energyis spent during production, it may be necessary to use other methods torecover the large quantities of hydrocarbons remaining in the reservoir.For example, a common technique is water flooding, wherein water isinjected through certain injection wells to displace the remaininghydrocarbons from the reservoir into a producing well in the field.

During production, the natural and/or artificial production fluidstravel up a casing (i.e., tubing) of the well. Commonly, the casing ofthe well includes lower sections of tubing having a smaller diameter,such as a diameter of 2⅞ inches, and upper sections having otherdiameters, such as a diameter of 5½ inches. Due to the larger dimensionsof the upper casing sections however, the fluid of the well may rise toa level such that the pressure behind the fluid is no longer sufficientto drive the fluids of the well to the surface. This causes the well toeffectively “suffocate.” Moreover, “bubbling” can occur, which resultsin significant gas loss (e.g., 3 to 10 MCF/day).

Commonly, gas wells are slim hole completions utilizing smaller diametercasing sections at the lower ends of the well. For example, consider acasing having a 500-1,000 foot section of 2⅞ inch tubing at the lowerend of the well, which then transitions into a 8,000-9,000 foot sectionof 5½ inch tubing extending to the surface. The 2⅞ inch tubing at thebottom of the casing may not enable the fluid to be forced up the lengthof the casing because the fluid essentially gets “too heavy”, especiallywhen the fluid reaches the 5½ inch portion of the tubing, or when thefluid includes a heavy substance, such as water. If the well becomes“waterlogged” and the fluid cannot be lifted to the surface, the wellsuffocates and bubbles.

Generally, a conventional pump with a string of solid rods cannot beutilized because of the inability of the convention pump to efficientlylift the heavy fluid. Further, caution must be used so as not to rupturethe casing wall of the well. Therefore, a need exists for a safe,effective and efficient pumping system for drawing fluid from aproducing well. It is to such a pumping system that the presentinvention is directed.

SUMMARY OF THE INVENTION

The pumping system of the present invention includes a down holedownstroke pump. Fluid flows into the barrel of the pump and isdisplaced therefrom via a hollow plunger into a string of hollow suckerrods on the downward stoke of the pump. The string of hollow sucker rodsextend generally to the surface so that the fluid can be directed tocollection equipment on the surface. Substantially all of the fluid isconveyed to the surface through the string of hollow sucker rods ratherthan through the cavity of the well tubing thereby relieving wear andtear on the sucker rods.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a pumping system constructed inaccordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1, shown therein is a pumping system 10 forpumping fluids from a gas well 12, the gas well 12 defined by a welltubing 14 (which may also be referred to herein as a well casing 14).The gas well 12 extends from a ground surface 15 a distance into theearth to a hydrocarbon bearing formation (not designated). The welltubing 14 has a well tubing hole 16 within which gases and fluids fromthe hydrocarbon bearing formation collect via perforations (not shown)in the well tubing 14.

The pumping system 10 is constructed of a pump 18 which has a pumpbarrel 20. A lower end 22 of the pump 18 is connected to a seatingnipple 24 which in turn is attached to a holddown device 26 which isattached to an inner surface 27 of the well tubing 14. The holddowndevice 26 thereby secures the pump 18 at a position within the welltubing 14. The seating nipple 24 has perforations 28 which allow fluidsand gas to flow into the pump 18 from the well 12.

The pump 18 is constructed of a hollow plunger 30 which has an upper end32 and a lower end 34. The hollow plunger 30 has a plunger cavity 36into which fluids and gas can flow from the pump barrel 20. Attached tothe hollow plunger 30 is a string of hollow sucker rods 38 which has alower end 40, an upper end 42, and a sucker rod cavity 43 into which afluid or gas can flow from the hollow plunger 30. The lower end 40 ofthe string of hollow sucker rods 38 is attached to the upper end 32 ofthe hollow plunger 30 via a hollow adaptor/connector 44. The hollowadaptor/connector 44 is constructed such that there is a substantiallycontinuous opening between the hollow plunger 30 and the string ofhollow sucker rods 38. Further, the pump 18, in one embodiment, isconstructed of a standing valve 46 having an entrance hole 48 and anexit hole 50, and a traveling valve 52 having an entrance hole 54 and anexit hole 56. The traveling valve 52 is connected to the lower end 34 ofthe hollow plunger 30. In operation, fluid and gas is pumped in anupward direction 60 through the string of hollow sucker rods 38 andthereby through a well head 66 and stuffing box 68 at an upper end ofthe well tubing 14 above the surface 15.

The fluid and gas flows therefrom into a flow T 70 which has a firstvalve 72 which leads into a separator 74, and optionally a second valve76 for inputting other materials into the flow T 70, if desired. Theupper end 42 of the string of hollow sucker rods 38 is attached to apolished rod 78 via a polished rod connector 80. The polished rod 78 isconnected to a pumping unit 82 which provides the mechanics for raisingand lowering the string of hollow sucker rods 38 and the hollow plunger30 of the pump 18 in a manner well known to those of ordinary skill inthe art.

Preferably, the pump 18 is a type of pump known in the art as adownstroke pump. In operation, the pumping system 10 is installed in thewell 12 such that the pump 18 is positioned at a position in the welltubing 14 where there is significant fluid collection, as discussedpreviously. As noted above, the pump 18 is preferably a downstroke pump,such as is commercially available from Skillman Pump Co., Tomcat Supply(the “Pup Pump,” Oklahoma City, Okla.), Norris O'Bannon Co., orHarbison-Fischer Manufacturing Co., for example.

The components of the well 12 and pumping system 10 are commerciallyavailable and/or are able to be manufactured or obtained by persons ofordinary skill in the art. For example, the pump 18 is preferably adownstroke pump such as a 2 inch by 1 1/16 inch “Pup Pump” availablefrom Tomcat Supply Co. in Oklahoma City. Other downstroke pumps areavailable as noted above.

In operation, the pump 18 shown in FIG. 1 pumps fluid and gas upwardlywhen the hollow plunger 30 of the pump 18 is on the downward stroke.More particularly, when the hollow plunger 30 is moving upwardly (pulledupwardly by the string of hollow sucker rods 38), the traveling valve 52is closed. The standing valve 46 is open and fluid fills the pump barrel20 as the hollow plunger 30 is lifted. When the downstroke is initiated,the hollow plunger 30 is pushed downwardly by the force of the string ofhollow sucker rods 38 causing the standing valve 46 to close and thetraveling valve 52 to open thereby causing the plunger cavity 36 of thehollow plunger 30 to be filled with the fluid in the pump barrel 20. Asfluid is forced into the plunger cavity 36, fluid already in the plungercavity 36 is forced upwardly in direction 60 into the string of hollowsucker rods 38. Eventually, as the string of hollow sucker rods 38 fillwith fluid over the entire length of the string of hollow sucker rods38, fluid is pushed through the flow T 70 into the separator 74 wherethe gas and oil can be separated from the remainder of the fluid pumpedfrom the well 12. Using the pumping system 10 described herein,substantially all of the fluid and gas is pumped through the string ofhollow sucker rods 38, contrary to other pumping systems previouslyavailable wherein fluid is pumped via the well tubing hole 16 (e.g., seeU.S. Pat. Nos. 6,497,561 and 6,368,084 issued to Skillman).

In one embodiment, the hollow sucker rod utilized for the string ofhollow sucker rods 38 can be a “PCPRod® 1000” hollow sucker rodobtainable from Tenaris Connections in Houston, Tex., and theadaptor/connector 44 can be a common 1 inch hollow rod connector havinga 11½ V thread which is modified to be compatible with the threading ofthe Tenaris PCPRod®. Examples of other threaded pipe joints whichconstructed to make the adaptor/connector 44 in accordance with thepresent invention can be found in U.S. Patent Application PublicationNos. 2004/0017079, 2004/0017080, and 2004/0113423; and U.S. Pat. No.6,764,108, the entire contents of each which are hereby expresslyincorporated herein by reference.

The stuffing box 68 is a device that prevents leakage around the stringof hollow sucker rods 38 as the string of hollow sucker rods 38 runsinto and out of the well 12. For example, the stuffing box 68 can be apacking or stuffing box made by J. M. Huber Corporation in Edison, N.J.or other stuffing boxes known in the art.

Because the string of hollow sucker rods 38 generally has a smallerouter diameter than the inner diameter of the well tubing 14 (e.g.,about 1.9 inches and 2⅞ inches, respectively), some bubbling can occurtherebetween. The stuffing box 68 may have an integrated stuffing flow T(not shown) which can be adapted to allow for collection of the gasbubbling in the annular side between the string of hollow sucker rods 38and the well tubing 14.

As noted above, the holddown device 26 is a device which holds the pump18 in a substantially stationary position within the well tubing 14.Preferably, the holddown device 26 is connected to a stationarycomponent of the pump 18 (e.g., the pump barrel 20) and/or the seatingnipple 24. In one embodiment, the holddown device 26 includes amechanical holddown having a packer, such as a commercially available 21/16 inch mechanical holddown.

Other components of the pumping system 10 may include, but are notlimited to, the following: a seating nipple 24 with dimensions 2 1/16inch by 2⅜ inch; an adaptor/connector 44 having internal and externaldimensions suitable for connecting the pump plunger 34 to an adjacentlydisposed hollow sucker rod of the string of hollow sucker rods 38constructed from PCP1000 hollow rods available from Tenaris. The flow T70 and stuffing box 68 are available from Tenaris. The stuffing box 68may be for example 2⅞ inches by 1.9 inches with a 1 inch bleeder. Wellheads 66 are well known in the art and are commercially available as areseparators 74. The well tubing 14 typically has an internal diameter of2⅞ inches and is well known to those of ordinary skill in the art.

From the above description, it is clear that the present invention iswell adapted to carry out the objects and to attain the advantagesmentioned herein, as well as those inherent in the invention. Althoughthe foregoing invention has been described in some detail by way ofillustration and example for purposes of clarity of understanding, itwill be apparent to those skilled in the art that certain changes andmodifications may be practiced without departing from the spirit andscope thereof, as described herein, and that the examples describedherein are not intended to limit the appended claims but only toexemplify several of the embodiments that the invention encompasses.

1. A pumping system for removing fluids from a well, comprising: a pumphaving a barrel and having a hollow plunger reciprocatingly disposedwithin the barrel; a string of hollow sucker rods having a cavity andextending from the pump to a well head near a surface end of the well; ahollow adaptor/connector for connecting the hollow plunger to the stringof hollow sucker rods, wherein the hollow adaptor/connector provides acontinuous opening between the hollow plunger and the string of hollowsucker rods; and wherein when the hollow plunger is raised on anupstroke of the string of hollow sucker rods, fluid enters the barrel ofthe pump and wherein when the hollow plunger is lowered on a downstrokeof the string of hollow sucker rods, the fluid in the barrel of the pumpis displaced into the cavity of the string of hollow sucker rods suchthat substantially all of the fluid pumped from the well into the barrelof the pump is introduced into the string of hollow sucker rods.
 2. Thepumping system of claim 1 further comprising a seating nipple attachedto a lower end of the pump.
 3. The pumping system of claim 2 furthercomprising a holddown device for connecting the seating nipple to aninner surface of a well tubing disposed within the well.
 4. The pumpingsystem of claim 1 wherein the pump is sized to fit with a well tubing ofthe well, the well tubing having an internal diameter of about 2⅞inches.
 5. The pumping system of claim 1 further comprising a stuffingbox positioned above the well head, wherein the string of hollow suckerrods reciprocates within the stuffing box.
 6. The pumping system ofclaim 5, wherein the stuffing box comprises an integrated stuffing flowT for allowing for the collection of fluids between a well tubing of thewell and the string of hollow sucker rods.
 7. The pumping system ofclaim 1 further comprising a flow T connected to the string of hollowsucker rods so that the fluid can be circulated from the string ofhollow sucker rods into a separator.
 8. The pumping system of claim 1further comprising a polished rod connected to and extending between aflow T or an upper end of the string of hollow sucker rods and a pumpingunit.
 9. A method of removing fluids from a well, comprising: providinga pumping system in a well, the pumping system comprising: a pump havinga barrel and having a hollow plunger reciprocatingly disposed within thebarrel, a string of hollow sucker rods having a cavity and extendingfrom the pump to a well head near a surface end of the well, and ahollow adaptor/connector for connecting the hollow plunger to the stringof hollow sucker rods, wherein the hollow adaptor/connector provides acontinuous opening between the hollow plunger and the string of hollowsucker rods; and operating the pumping system in the well such that whenthe hollow plunger is raised on an upstroke of the string of hollowsucker rods, fluid from the well enters the barrel of the pump and whenthe hollow plunger is lowered on a downstroke of the string of hollowsucker rods, the fluid in the barrel of the pump is displaced into thecavity of the string of hollow sucker rods such that substantially allof the fluid pumped from the well into the barrel of the pump isintroduced into the string of hollow sucker rods and is driven via thestring of hollow sucker rods into a collection device.
 10. The method ofclaim 9 wherein in the step of operating the pumping system, thecollection device is a separator.
 11. The method of claim 9 wherein inthe step of providing the pumping system, the pumping system furthercomprises a seating nipple attached to a lower end of the pump.
 12. Themethod of claim 11 wherein the pumping system further comprises aholddown device for connecting the seating nipple to an inner surface ofa well tubing disposed within the well.
 13. The method of claim 9wherein in the method of providing the pumping system, the pump of thepumping system is sized to fit with a well tubing of the well, the welltubing having an internal diameter of about 2⅞ inches.
 14. The method ofclaim 9 wherein in the method of providing the pumping system, thepumping system further comprises a stuffing box positioned above thewell head, whereby the string of hollow sucker rods reciprocates withinthe stuffing box.
 15. The method of claim 14 wherein the stuffing box ofthe pumping system comprises an integrated stuffing flow T for allowingfor the collection of fluids between a well tubing of the well and thestring of hollow sucker rods.
 16. The method of claim 9 wherein in themethod of providing the pumping system, the pumping system furthercomprises a flow T connected to the string of hollow sucker rods so thatthe fluid can be circulated from the string of hollow sucker rods intothe collection device.
 17. The method of claim 9 wherein in the methodof providing the pumping system, the pumping system further comprises apolished rod connected to and extending between a flow T or an upper endof the string of hollow sucker rods and a pumping unit.